Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $95.93   12.217%   $107.6498   $107.65   $107.65   $107.60  
  Purchase #2 $47.93   4.783%   $50.2225   $50.22   $50.20   $50.20  
  Purchase #3 $13.76   3.473%   $14.2379   $14.24   $14.25   $14.20  
  Purchase #4 $161.38   7.270%   $173.1123   $173.11   $173.10   $173.10  
  Purchase #5 $226.79   4.461%   $236.9071   $236.91   $236.90   $236.90  
  Purchase #6 $118.76   4.747%   $124.3975   $124.40   $124.40   $124.40  
  Purchase #7 $187.66   10.305%   $206.9984   $207.00   $207.00   $207.00  
  7 purchase totals = $852.21       $913.5255   $913.53   $913.50   $913.40